Combustion Behaviors of Emulsified Hydrocarbons and JP-4/N₂H₄ Droplets at Weightless and Free Falling Conditions

Abstract

Combustion behaviors, mainly focused on the secondary micro-atomization phenomenon of oil-in-water (O/W) and water-in-oil (W/O) hydrocarbon emulsion droplets, were observed under weightless conditions, and compared with the combustion behaviors of free-falling emulsion droplets under the effect of gravitation. Experimental results are reported on the burning of droplets of pure n-paraffine (C₅-C₁₅), gas-oil, kerosene, JP-4, and O/W type JP-4/N₂H₄ emulsions suspended on a quartz tip. It was found that under weightless (zero gravity, no buoyancy) conditions in air no violent micro-explosion would occur with regard to n-tridedane, -tetradecane, -pentadecane, gas-oil, and JP-4 emulsions, but, for all of them, the onset of micro-explosions resulting in instantaneous droplet disruption was observed in quiescent air or free-falling combustion in oxygen enriched atmospheres under one gravity. “Spray-like” and non-disruptive micro-atomization under weightless conditions and importance of gravity which promotes the micro-explosion are described.